Case Experiments:
Zero Run Conducted After Run 8 ….. 22MAY98
The day after Run 8 was completed, we performed a zero run to check our calorimeter. The following plot shows the results:
For this run, Pin and Pout are plotted on a -4 to +6 watt scale (1 watt/div) with P=0 at the 4th vertical division from the bottom.
As you can see from the Pout trace, the system slowly equilibrates with about a 1 hour time constant. After 5 hours, the Pout trace is essentially flat.
For the last 4 hours of the run, the average Pout was -0.03 watts, an excellent zero reading for a calorimeter that is being used to measure 20 watt experiments.
Details:
The Pout trace exhibits random noise about +/- 0.1 watts in magnitude. This noise is apparently a direct result of small variations in the temperature of the inlet water to the heat exchanger (Tin).
To explore this relationship, Tin has been plotted on a 10X expanded scale that runs from 39.5° C to 40.5° C (0.1° C/div) with zero in the center of the plot.
The Tin trace runs nominally down the center of the plot and you can see that the major deviations in it are more-or-less inversely correlated with similar deviations in Pout. This is not surprising, as Pout is directly dependent upon Tin.
Note that the Tin trace shows an overall stability of +/- 0.02° C or better over most of the run.